The present invention relates to equipment for stranding elongated stock and is specifically provided for purposes of making cable or the like of stranded configuration, whereby particularly a plurality of stranding elements are combined to a unit. Equipment of the type to which the invention pertains includes broadly at least one carrier which is rotatable about its own axis. In practice, multiple carriers carry separately stores of stranding elements; in addition, such equipment includes a stranding head or nipple which combines the several stranding elements traversing the head and nipple accordingly. A take-up spool is provided downstream from the nipple for receiving the stranded stock, the spool being likewise rotatable about its axis. The stores of the individual stranding elements may be provided as coils with or without any rotating spool support element. In the latter case, the coils are contained inside containers which are effectively connected and fastened to a carrier such that the coil axes run obliquely to the axis of rotation of the respective carrier element, the stranding element being withdrawn from the center of the coil of the respective container.
Stranding machines of the type outlined above are, for example, used in the manufacture of electrical cables and conductors, including communication cables, power cables, or the like; however, the same technique can be employed for stranding filaments into wires or for stranding certain elements including already stranded elements into load-carrying cables. Generally speaking, one can see that these stranding elements may be electrical elements, wires, pairs, quads, and stranded bundles in which individual wires or filaments are combined so that, ultimately, stranding is a multistage process, in which stranding elements of one level of stranding have themselves been stranded in a preceding level.
Known equipment includes so-called stranding baskets which are rotatable about their axes but being provided with rotatable spool bodies, upon which are wound the stranding elements. Such an arrangement is disadvantaged by of the fact that the stranding baskets as well as the spool bodies are relatively heavy, which means that the system operates with large rotating masses. This, of course, presents considerable dynamic difficulties which are taken care of by rather extensive and expensive construction. Stranding equipment is known in which the stranding elements are twisted and stranded together at alternating pitch. This method is also known as SZ-stranding. One uses stationary stores for the stranding elements from which they are taken and combined in a stranding nipple, whereupon the combined stranding elements are wound upon a rotating spool element. For reversing the twist, the take-up spool alternates its direction of rotation. Stranding with reversing pitch and twist has the advantage over stranding by means of uniform twist that one does not need rotating stranding baskets containing the stranding elements. Such baskets or containers limit the length of the stranding elements; and under consideration of rather extensive centrifugal forces, these baskets have to be dimensioned accordingly, even though the storage capacity is limited. This, of course, is obviated by the SZ-method. In fact, the SZ-stranding method permits a continuous production mode at a rather high throughput speed. On the other hand, the reversing mechanism required for practicing the method is rather extensive and expensive. Moreover, the stranding elements as combined have to be held together in some fashion on account of the reversing of the stranding direction.
The last-mentioned state of the art is improved by the German printed patent application No. 30 35 208 (see U.S. Pat. No. 4,407,116), which discloses more particularly the point of departure of the present invention. The bodiless coils used for storing the stranded stock, as per this particular publication, are constituted by coiled stranding elements which have been wound without employment of a coil carrier. The stranding equipment disclosed in this reference provides uniform direction of rotation and, therefore, uniform twist and is relatively simply constructed because one does not need here rotating coils for the stranding elements. The bodiless coils, in which the stranding elements are assembled, are, however, subject to mechanical interference because shaking of the machine tends to loosen the coil loops. This is particularly the case if the coils are not oriented on a vertical axis, but are held in a horizontal or near horizontal position of the coiling axis. Upon installing these coils in the stranding machine, the stiffness of the stranding elements suffices to keep the individual loops apart. Also, if there are only minor shocks and shakings experienced during operation, the loops will remain adequately separated. This, however, is not true if shocks are experienced which cannot be avoided, particularly in case the machine runs at a high production speed. Since now the individual loops may fall off and become intertwined, the stranding machine may well tear such stranding elements.